The present invention relates to an arrangement for producing dispersion layers on the inner surfaces of hollow cylinders open at least on one side thereof, especially on contact or slide surfaces in cylinders for internal combustion engines, whereby an electrolyte together with the solid particles to be deposited are conducted over the surface to be coated at the outer circumference of an anode centrally arranged in the cylinder axis and the electrolyte is introduced into the cylinder with the aid of a swirl-producing flow body.
The DE-OS 22 61 776 describes a known arrangement. In this prior art arrangement, a very high swirl or vortex flow is produced for increasing the build-up rate of the solid particles at the surfaces to be coated. The build-up rate can be considerably increased therewith. However, only a build-up rate uniform over the entire length of the surface to be coated is achieved therewith.
Investigations in cylinder slide or contact surfaces of reciprocating piston internal combustion engines have indicated that within the area of the upper reversing point of the piston, an increased wear occurs at the cylinder contact or slide surfaces.
In order to reduce this wear, one could provide by means of the known process an increased build-up rate of the wear-preventing solid particles over the entire cylinder contact or slide surfaces. This, however, makes sense only for small series. In case of large series and/or multi-cylinder large-volume internal combustion engines, this represents a very uneconomical procedure because correspondingly many wear-reducing solid particles would have to be deposited at surfaces, and more particularly in such a thickness as is not necessary.
It is the object of the present invention to further develop an arrangement of the aforementioned type to the effect that deliberately controlled differently dense build-up rates of the wear-reducing solid particles is made possible in a single operating step.
The underlying problems are solved according to the present invention in that the swirl-producing flow body conducts the electrolyte in such a manner that the flow splits off into a laminar and turbulent flow component. The present invention is based on the recognition that with the aid of a turbulent flow an increased build-up rate of the wear-reducing solid particles can be achieved. Care should therefore be taken at the requisite places that a turbulent flow of the electrolyte is maintained thereat. As soon as this turbulent flow converts itself into a laminar flow, the build-up rate of the solid particles is reduced. One achieves then a considerably thinned-out dispersion layer which, however, corresponds to the reduced wear requirements. An economic procedure is achieved thereby because the more wear-resistant concentric layers are produced only where they are absolutely necessary.
According to another feature of the present invention, the flow body includes within the plane of the inflow a spirally shaped annular channel for the electrolyte which is in communication with a swirl or vortex chamber by way of an overflow channel arranged obliquely to the hollow cylinder longitudinal axis. This arrangement of the flow body permits the realization of a turbulent flow at the inlet and subsequently a laminar flow at the surfaces to be coated.
An accurately defined and reproducible boundary between the different concentrations of the wear-resistant layers can be achieved if the swirl chamber is constructed as circumferential annular channel with circularly shaped cross section and having a circumferential deflection nose, as viewed in the flow direction. This boundary is marked by a change from the turbulent to the laminar flow.
According to still other features of the present invention, the flow body is arranged outside of the hollow cylinder and is sealingly connected with the same and is constructed at the same time as anode support while the swirl chamber is constructed two-partite wherebY the lower part connected with the overflow channels is formed by the flow body itself and the upper part by the anode. A flow body constructed in such manner is particularly suited for use with cylinder contact or slide surfaces of reciprocating piston internal combustion engines. It is assured thereby that only the cylinder contact or slide surfaces which are to be coated will, in fact, also be coated. All of the remaining parts of the crankcase forming the cylinder contact or slide surfaces are not unnecessarily coated.